Each of these practices are hacks which make website setups more complex and more opaque, but with the goal of speeding up front-end performance by working around limitations in HTTP. Fortunately, these somewhat ugly practices are no longer necessary with HTTP/2.

Importantly, Matt Wilcox points out that in an HTTP/2 world, these practices might actually slow down your website, for the following reasons:

If you serve concatenated CSS, Javascript or image files, it's likely you're sending more content than you strictly need to for each page

Serving assets from different domains prevents HTTP/2 from reusing existing connections, forcing it to open extra ones

But not yet...

This is all very exciting, but note that we can't and shouldn't start changing our practices yet. Even server-side support for HTTP/2 is still patchy, with nginx only promising full support by the end of 2015 (and Microsoft unusually leading the way).

As usual the main limiting factor will be waiting for market share of older versions of Internet Explorer to drop off. Braver organisations may want to be progressive by deliberately slowing down the experience for people on older browsers to speed up the more up-to-date and hence push adoption of good technology.

If you want to get really clever, you could serve a different website structure based on the user agent string, but this would really be a pain to implement and I doubt many people would want to do this.

Even with the most progressive strategy, I doubt anyone will be brave enough to drop decent HTTP/1 performance until at least 2016, as this is when nginx support should land; Windows 10 and therefore IE 11 will have had some time to gain traction and of course Internet Explorer market share in general will have continued to drop in favour of Chrome and Firefox.

TL;DR: We front-end developers should be ready to change our ways, but we don't need to worry about it just yet.